I love to race and I love to race well. I despise the feeling after a poor race and thinking "if I had only trained more.." So, even when the day to day grind of training, (as it sometimes feels) when the weather is less than ideal, or you're tired, or have other things to do, I think back to a bad race and I get out there to get some miles in. And more times than not, one you get dressed and out on the roads you feel great.
In your case, injury recovery....I've been there, many a time. I've endured several lower leg and foot stress fractures. My first in college, I also gained weight, but mostly muscle since I used my extra time and energy in the weight room. I tried to spend time on the bike or in the pool but I was easily bored by it.
The key is to come back slowly and listen to your body. As runners, we are "tough" and often run through pain because we can and because most pain start out minor. DONT DO IT. Take it from me and may runners before me, when you feel a ding or nick, address it, rest, ice, figure out what is causing it. A small step back, even though it is hard to accept is better than the GIANT step back that a serious future injury will be.
So remember this feeling of dread and unhappiness with being injured and think of it the next time you feel you can "run through" the pain.
I wish you luck in your training.
Run Smart, Run Far, Run Fast
http://brooklynrunning.wordpress.com